Mortgage Loans Individually Impaired Loans - 2 (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	$ 97,988
Individually impaired loans with no related allowance recorded: total interest income recognized	270
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	1,023
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	95
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	31
Individually impaired loans with no related allowance recorded: average recorded investment	18,545
Impaired Financing Receivable, Average Recorded Investment	116,533
Individually impaired loans: total interest income recognized	1,293
Impaired Financing Receivable, Interest Income, Cash Basis Method	126
Single-family [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	97,741
Individually impaired loans with no related allowance recorded: total interest income recognized	268
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	1,021
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	95
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	31
Individually impaired loans with no related allowance recorded: average recorded investment	18,192
Single-family [Member] \| Other [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	19,898
Individually impaired loans with no related allowance recorded: total interest income recognized	48
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	204
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	15
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	3
Individually impaired loans with no related allowance recorded: average recorded investment	3,000
Single-family [Member] \| FixedRateResidentialMortgage15yearMember
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	1,323
Individually impaired loans with no related allowance recorded: total interest income recognized	4
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	12
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	1
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	1
Individually impaired loans with no related allowance recorded: average recorded investment	318
Single-family [Member] \| Fixed Rate Residential Mortgage 30 and 20 year Member
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	76,400
Individually impaired loans with no related allowance recorded: total interest income recognized	212
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	804
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	79
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	26
Individually impaired loans with no related allowance recorded: average recorded investment	14,474
Single-family [Member] \| Adjustable Rate Residential Mortgage
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	120
Individually impaired loans with no related allowance recorded: total interest income recognized	4
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	1
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	1
Individually impaired loans with no related allowance recorded: average recorded investment	400
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Individually impaired loans with related allowance recorded: average recorded investment	247
Individually impaired loans with no related allowance recorded: total interest income recognized	2
Table Footnote [Abstract]
Individually impaired loans with related allowance recorded: total interest income recognized	2
Individually impaired loans with related allowance recorded: interest income recognized on a cash basis	0
Individually impaired loans with no related allowance recorded: interest income recognized on a cash basis	0
Individually impaired loans with no related allowance recorded: average recorded investment	$ 353

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